It is perhaps worth showing an example using the advdate package, mentioned by Villemoes, as it has a single command solution for this, \DayAfter[n], which prints the date n days ahead and leaves \today unchanged on exit. So for 7 days ahead:

the advdate package also provides separate macros \AdvanceDate to change the value of \today to a number of days ahead together with \SaveDate and \SetDate to save and set the current value used for \today. texdoc advdate gives full details for these and other macros in the package, as usual.